If you find yourself visiting Paris at some point and you own an Android phone, I recommend installing the following apps: Paris Metro Bus Train (offline public transportation maps), Paris City Guide (offline city guide by TripAdvisor) and Google Maps. The last app is probably already installed on your phone, but if it’s not, get it now. In Google Maps you can, very conveniently, download maps and use them offline, thus preventing blowing your vacation budget on mobile data costs. The TripAdvisor app also has offline maps, but in my humble opinion, the Google maps worked better.